One aspect relates to a light guide comprising a jacket and one or more cores, wherein the jacket surrounds the cores. Each core has a refractive index profile perpendicular to the maximum extension of the core, wherein at least one refractive index n.sub.K of each refractive index profile is greater than the refractive index n.sub.M1 of the jacket. The jacket is made of silicon dioxide and has an OH content of less than 10 ppm, a chlorine content of less than 60 ppm, and an aluminium content of less than 200 ppb. One aspect also relates to a silicon dioxide granulate I, characterized by a chlorine content of less than 200 ppm and an aluminium content of less than 200 ppb, in each case based on the total weight of the silicon dioxide granulate I.

The invention relates to a process for the preparation of a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate obtainable from a silicon dioxide powder, wherein the silicon dioxide granulate has a larger particle size than the silicon dioxide powder, ii.) Making a glass melt out of silicon dioxide granulate and iii.) Making a quartz glass body out of at least part of the glass melt, wherein the melting crucible has at least one inlet and at least one outlet, wherein at least part of the glass melt is removed via the melting crucible outlet. The invention further relates to a quartz glass body which is obtainable by this process. The invention further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

The invention relates to a process for the preparation of a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt out of the silicon dioxide granulate and iii) Making a quartz glass body out of at least part of the glass melt, wherein the provision comprises the steps I. Providing a silicon dioxide powder with at least two particles made from a silicon-chlorine compound, II. Bringing the silicon dioxide powder into contact with steam to obtain a treated silicon dioxide powder and III. Granulating the treated silicon dioxide powder to obtain a silicon dioxide granulate, and wherein the chorine content of the silicon dioxide powder is greater than the chlorine content of the silicon dioxide granulate. The invention further relates to a quartz glass body which is obtainable by this process. The invention further relates to a process for providing a silicon dioxide granulate. The invention further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate composed of a pyrogenic silicon dioxide powder, making a glass melt out of the silicon dioxide granulate and making a quartz glass body out of at least part of the glass melt. The quartz glass body has an OH content of less than 10 ppm, a chlorine content of less than 60 ppm and an aluminium content of less than 200 ppb. One aspect also relates to a quartz glass body which is obtainable by this process. Furthermore, one aspect relates to a formed body and a structure, each of which is obtainable by further processing of the quartz glass body.

One aspect relates to a process for the preparation of a quartz glass body, including provision of a silicon dioxide granulate, making a glass melt from the silicon dioxide granulate and making a quartz glass body from at least part of the glass melt. The provision includes making a silicon dioxide powder with at least two particles prepared from a silicon-chlorine compound, bringing the silicon dioxide powder into contact with ammonia to obtain a treated silicon dioxide powder, and granulating the treated silicon dioxide powder to obtain a silicon dioxide granulate. The chlorine content of the silicon dioxide powder is greater than the chlorine content of the silicon dioxide granulate. One aspect relates further to a quartz glass body which is obtainable by this process. One aspect also relates to a process for the preparation of a silicon dioxide granulate.

The present disclosure concerns expandable silica particles having a coating comprising talc powder and kaolin powder provided on the outer surface of the expandable silica particle and expandable and expanded silica particles comprising silica fume and/or ultrafine quartz silica sand beneath the surface of the particles. Methods for producing expandable and expanded silica particles are disclosed, including a method using a vibration plate and a furnace having a vibration plate for carrying out that method. The expanded silica particles have high compressive strength, substantially uniform cell size and distribution, low water absorption, and low porosity on the outer surface. They are useful as a filler in matrix materials, like concrete or epoxy, as insulation material with various binder materials, and as water filtration medium.

Foamed glass beads can be made from glass, a hydrated foaming agent, a hydrated binding agent, a sealing agent, a fluxing agent, and a solvent. The hydrated binding agent can hold the glass and the hydrated foaming agent in solution. The glass can be derived from glass cullet that is ground into powder. The glass powder, the hydrated foaming agent, the hydrated binding agent, the sealing agent, the fluxing agent, and the solvent can be mixed together to create a preform material that is pelletized to make preform pellets. The preform pellets can be dried and then heated to a predetermined temperature. The heating process can create the final, foamed glass beads.

A method for producing synthetic quartz glass by fusion of SiO.sub.2 granulate involves synthesizing amorphous SiO.sub.2 primary particles, granulating the amorphous SiO.sub.2 primary particles to form an open-pore SiO.sub.2 granulate, sintering the open-pore SiO.sub.2 granulate by heating in a sintering atmosphere at a sintering temperature and for a sintering period to form a densified SiO.sub.2 granulate, and melting the densified SiO.sub.2 granulate at a melting temperature to form the synthetic quartz glass. To provide an inexpensive production of low-bubble transparent components of quartz glass despite the use of still open-pore SiO.sub.2 granulate, the sintering atmosphere, sintering temperature and sintering duration are adjusted such that the densified SiO.sub.2 granulate still comprises open pores but manifests a material-specific infrared transmission T.sub.1700 at a wavelength of 1700 nm. This transmission is in the range of 50-95% of the infrared transmission T.sub.1700 of quartz glass granules of the same material.

A glass, glass-ceramic, or ceramic bead is described, with an internal porous scaffold microstructure that is surrounded by an amorphous shield. The shield serves to protect the internal porous microstructure of the shield while increasing the overall strength of the porous microstructure and improve the flowability of the beads either by themselves or in devices such as biologically degradable putty that would be used in bone or soft tissue augmentation or regeneration. The open porosity present inside the bead will allow for enhanced degradability in-vivo as compared to solid particles or spheres and also promote the growth of tissues including but not limited to all types of bone, soft tissue, blood vessels, and nerves.

The invention relates to a process for producing SiO.sub.2 granules by freezing and re-thawing an SiO.sub.2 suspension, wherein a separation of liquid and sediment composed of agglomerated SiO.sub.2 particles occurs in the course of thawing, the liquid removed is decanted and the residual moisture in the sediment is removed by a drying step with formation of the SiO.sub.2 granules. According to the invention, an auxiliary comprising alkali metal-free bases in the form of nitrogen hydrides is added to the suspension to set the pH greater than 7.